During 25 years the four crops of maize, oats, wheat, timothy and clover hay have been taken in rotation from the four tiers of plats at the Pennsylvania State College, so that the influence of the soil has been entirely eliminated. At the December farm prices for the decade ending December 1, 1906, the value of these four crops per acre have been: Maize, $29.67; oats, $14.49; wheat, $18.49; and hay, $18.05. It will be noted that during 25 years the average income from an acre of maize has been almost exactly twice that from an acre of oats. The region where these results were obtained is relatively unfavorable to a large yield of maize. It is obvious, therefore, that a modification in the rotation may modify the average income from the farm materially, provided such modification does not reduce the fertility of the soil. Thus, while the average income per acre during 25 years for the four-course rotation above mentioned was $20.17, if the rotation were increased to a five-course rotation by the addition of another year of maize, the average income would be $22.45 an acre. It may be desirable to modify the rotation in order to increase or decrease a certain crop usually fed upon the farm. Thus, with a four-course rotation of maize, oats, wheat, clover and timothy, one-fourth the area would produce hay; while with a six-course rotation, composed of maize, oats, wheat, each one year, and hay three years, one-half the area would produce hay. If it is desired to still further reduce the area in oats and wheat, a seven-course rotation could be arranged with maize, two years in succession. This is the rotation that would be desirable for a dairy farm where it is planned to keep as many cows as practicable and to buy the concentrates largely. Either the wheat or the oats could be taken out of this rotation if either the one or the other were thought undesirable and a still greater amount of roughage desired. On the other hand, there are places where the minimum amount of roughage is wanted. There are certain sections of the central West where it is possible to sow oats on corn stubble without plowing and where occasionally a rotation is practiced of maize, oats and mammoth clover. The clover is plowed for maize, the oats are disked in upon the corn stubble and the next year the clover is pastured until about June 1, when it is allowed to go to seed. In this rotation the only roughage obtained is the corn stover and the oat straw. Another result reached by this rotation is that only one-third the land is plowed annually. In the four-course rotation mentioned above three-fourths of the land must be plowed, while in the six-course rotation one-half is plowed each year. In other ways the character of the rotation modifies the labor. For example, the labor and cost of harvesting an acre of hay is much less than that of producing, harvesting and threshing an acre of wheat.